I saw a gang of 3 phase variacs for a reasonable price ($15) at the local
electronics surplus/supply place.  However, the variacs are 400Hz instead
of 60Hz.  Does anyone know if they will work ok for 60Hz?  I thought the
main considerations with different frequencies for transformers are eddy
current losses.  If that is true, wouldn't a transformer for a higher
frequency work fine for a lower one?